1. Field of the Invention
The present invention relates to the alignment and focusing of a camera with respect to an object plane and, more particularly, to the alignment and focusing of a camera with a solid state image sensor with respect to a desired location on an object plane.
2. Description of the Prior Art
A major problem in applying, for example, linear array type cameras for copy work have historically been the alignment of the camera so that the camera's measurement line or sensor line is positioned as desired at the object. To locate the measurement line users have often resorted to probes or specially designed targets. With these tools the user will generally observe the camera signal and try to locate a few points along the measurement line and the ends of the line. Unless great care is exercised, this is difficult to do. Some camera manufacturers have resorted to optical viewfinders such as are included in commercial photographic cameras to aid alignment. Unless this viewfinder is precisely constructed itself, including a precision reticle marking the measurement line, the viewfinder is of little value for other than coarse alignment.
A patent of interest for its teaching is U.S. Pat. No. 3,992,108, entitled "Optical System Alignment Apparatus" by W. L. Kidd et al. In that patent there is disclosed a pair of scan lamps which are used in an electrophotographic printing machine. The scan lamps are mounted in a housing which is moved from one position to another to form an overall image. An alignment member is placed on the housing containing the scan lamps and the light reflected from the alignment member is projected onto an indicating means. Alignment of the scan range of the scan lamp can then be adjusted by observing the projected alignment member's image onto a centrally located calibration mark on the indicating means.
Another patent of interest for its teaching is U.S. Pat. No. 4,084,184, entitled "TV Object Locator and Image Indentifier" by D. W. Crain. In that patent the alignment of a TV camera having a lens axis is accurately aligned to an object by determining through, for example, acoustical sonar, the accurate position of the object and then determining the axis of the TV lens and controlling the position of the TV axis to correspond to the position of the object.
In U.S. Pat. No. 4,280,135 entitled "Remote Pointing Systems" by H. R. Schlossberg there is disclosed a system which permits a lecturer to use a laser beam pointer projected onto a projected image to highlight areas to be emphasized in a presentation. The pointer position can then be transmitted to either locations where the projected image is being viewed so that audiences at multiple locations can see the same presentation as that seen at the original location.